Choose the coasts that are running along the Arabian sea.

a. Northern Circars

b. Malabar

c. Konkan

d. Coromandel

To determine which of the given coasts run along the Arabian Sea, let's examine the geographical location of each coastal plain of India:

1. Malabar Coast (b): This is the southern part of the western coastal plain of India, extending along the southwestern coast of the Indian peninsula, primarily in Kerala. It faces the Arabian Sea.

2. Konkan Coast (c): This is the northern and central part of the western coastal plain of India, extending along the western coastline of Maharashtra, Goa, and parts of Karnataka. It also faces the Arabian Sea.

3. Northern Circars (a): This is a region of the eastern coastal plain of India, lying between the Mahanadi and Krishna rivers in Andhra Pradesh and Odisha. It faces the Bay of Bengal.

4. Coromandel Coast (d): This is the southern part of the eastern coastal plain of India, extending along the southeastern coast of the Indian peninsula, primarily in Tamil Nadu. It faces the Bay of Bengal.

Based on this geographical division, the coasts running along the Arabian Sea are the Malabar Coast (b) and the Konkan Coast (c). Therefore, the correct option is "Only b and c".